The present invention relates generally to multimedia computer applications, and more particularly to the synchronized presentation of signals such as video and audio signals.
An increasing fraction of video presentations are computer-generated motion pictures and synchronized audio such as those produced with the QuickTime system of Apple Computer, Inc. (QuickTime is a registered trademark of Apple Computer, Inc.). Such multimedia presentations may be used for promotional, instructional or entertainment purposes. Often times, a multimedia presentation made with a comparatively expensive computer system is desired in a more ubiquitous format such as VHS consumer video tape. The present invention is an arrangement of computer hardware and software that allows video and audio information resident on the computer to be transformed to video and audio signals that may be viewed directly or recorded on video tape.
For the purpose of computer processing, synchronized video and audio data are currently kept in separate files. Time codes, which are binary sequences inserted into these files, are used to indicate the timing of the video and audio data, which are synchronized by being locked to a common time code reference. Examples of time codes that can be used are Society of Motion Picture and Television Engineers (SMPTE) and European Broadcasting Union (EBU) time codes.
Computer-stored video and audio presentations have heretofore been reproduced using independent video and audio interfaces as input-output (I/O) devices. The video and audio data are read from a mass storage device into random access memory (RAM) buffers in the main memory using separate I/O processes and held in the main memory at the same time. Separate I/O processes are then used to transfer the data from the main memory to the video and audio interfaces. The system must be fast enough to provide the data at rates corresponding to the sampling rates of the audio and video signals. While this approach allows the most general sort of image and sound manipulations, it is also expensive to implement due to the high processing and I/O speeds required.
Accordingly, an object of the present invention is to provide a system for transferring data to video and audio interfaces using a single I/O device.
Another object of the present invention is to provide a method for storing and presenting synchronized video and audio signals using and reading a single file.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.